<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <meta charset="UTF-8">
    <title>响应式布局</title>
    <link rel="stylesheet" href="css/index.css">
</head>
<body>

<header></header>
<main>
    <div class="left"></div>
    <div class="center"></div>
    <div class="right"></div>
</main>
<footer></footer>

<!--遮罩视图-->
<div class="mask">
    对不起，该网页暂不支持屏幕分辨率小于 400 x 450 下的显示！
</div>


</body>
</html>









































